We're going back to the moon. It may be 15 or 20 years until we get there, but NASA is headed that direction. Many people, including a lot of astronomers, are opposed to this new lunar exploration. It will be very expensive, and we aren't sure what the point of the exploration is.
A colleague of mine once argued that we astronomers should be pushing NASA to build a telescope on the moon once we return. His idea, a liquid-mirror telescope, is pictured above. Such a telescope would be quite expensive, and the science it could do may be able to be done more cheaply with orbiting telescopes. But the point was that NASA is much more likely to spend a lot of money on the moon, not on new space telescopes, and if astronomers want a piece of that money, the time to start lobbying is now. Otherwise, we could find ourselves out in the cold once lunar exploration ramps up.
It's sort of like a parent shopping at a high-end luxury store asking their thrifty teenager, "Hey, should we buy you this 2nd-generation iPhone for $500?" The teenager responds, "But we can go to the Apple Store and buy the new iPhone 3G, which is more functional and less then half the price!" To which the parent responds, "You're getting this phone or you're getting nothing." What should the kid do? I think most of us would be tempted to take the phone.
Today, Space.com posted an article on a new design for a lunar telescope that has been proposed. This telescope could be built from materials on the moon. I have no doubt that the cost would be very high and the design technologically challenging to build (as would be the liquid-mirror telescope my colleague proposed). I know very little about the new proposal, such as what wavelengths of light it would be best suited for, or what instruments would go on it, or what scientific question(s) it would address. And, no doubt, NASA would make sure it is a very nice telescope, in terms of these capabilities.
But I wonder if we astronomers need to start thinking much harder about this. Do we want to push for a telescope on the moon? If there is a trade-off between a lunar telescope and a more functional, less-expensive space-based telescope, then let's by all means choose the latter. But I do think it is likely that we might be given the choice of a big lunar telescope, or no big telescope at all. And if we wait 15 years to make up our minds, it will be too late. Who knows what the astronauts will be doing on the moon science-wise, but it certainly won't be astronomy. And we'll have missed out.
There is good astronomy that can be done on the moon. One of the most convincing ideas I've heard is to put a radio telescope on the far side of the moon; the moon will block out radio signals from Earth, allowing us to study signals from space that are currently swamped by our FM radios, our iPhones, our satellite TV, and most every other modern bit of wireless communication. Some types of astronomy, like optical astronomy and, perhaps, infrared astronomy, are better done in orbit so that we don't have to worry about astronaut dust and other activity upsetting the instruments. But both of these fields would not suffer from a lunar telescope.
Astronomers are beginning to assemble our "decadal survey," a 10-year look into the future needs and desires of astronomy. This survey is cited in our funding requests to Congress and NASA. Maybe this time around we should debate the various possibilities of lunar telescopes. If we wait until 2020 to ask, it may be too late.